Vehicle detecting arrangement suitable for use in traffic control systems



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VEHICLE DETECTING ARRANGEMENT SUITABLE FOR USE IN TRAFFIC CONTROL SYSTEMS Filed June 19, 1950 5 Sheets-Sheet 5 IN VEN TORS.

Jflazzlesliafi (a 6? BY .E'hzesi 7Z0 0 A T TORN E YS Patented July 15, 1952 Qumran srArEs PATENT OFFICE ,VEHICLE DETECTING ABLE 'FOR USE IN SYSTEMS ARRANGEMENT SUIT TRAFFIC CONTROL Alan .Leslie'. Rangeand Ernest z'Ehorpe; Liverpool, England, assignors to Automatic,- Telephone. &

.-.Electric Company ..a-British company =App'lication'June' 19,

'In Great'Britai .5 Claims. (01. 177+337) been solved completelysatisfactorily and. it. has

som'e'timesahappened that detectors have developed faults which result in the permanent closure --:.of "the" ele'ctrical signalling circuit. Such .faults cannot alwaysbedealt with immediately and in th'e' meantime the operation of the system. is

preju'clicedsince the effect ofsuch .a' faulty 'Jdeate'ctor' is to procure rightof way for a maximum period for the "traflic lanewconcernedeven in the absence" of traflic thereon, and this will delay tr'al'fiic on other approaches and thus tend to tnullifys the advantages which a trafiic-actuated -rsignallingfsystem"is intended to secure. :It isone ot 1 the features of .the present invention that, ithoughthe normal operation" of the detector unit "nwillthaveithe; operating characteristics usually :-consideredzdesirable,if: afault of the type-referred wtoaabove :shoulddevelop, .the operation-will not-be seriously disturbed during the time which elapses rhefore the faultcanz be put, right.

According tooneieatu-re .of the invention the wrelayswhich responds to :the passage-of a vehicle ris connected rin-.circuit with a capacitor in such -manner. that only a single relay operation lastingfora-a-definite time period takesplacehowever long thecontacts. operated from the detector remain-closed. fThis operation may. be modified if necessary. by: the? provision of 1 a, locking circuit. 'iThe dctectorcircuit-fis moreover-connected tadifaterenturelays according as the. traffic phaseconcerned :is: or :iS :not in'possession: of right ofway :-*-.-.and;:the r'e1ay:connected. up while the phase .in ues'tion iS'iIIIIlOSSBSSlOIl'Of right of way may-be .wcommomto'all .the various phases. and connection is anadentheretoi overa .crossvconnecting frame so nthat'iextensionmayreadily be provided for some rrphases' and .not others, for instance pedestrian gi pha'ses. I 1

iiA.-'f11rther" advantage. of the -.arrangementac- ;cordingxtozzithe :presentuinvention is that; a: unircdirectionalnharacteristic can beprovided with a- Limited, Liverpool, England,

1950; Serial-No."168,876 11 August: 18; 1949 .:minimum of equipment and-moreoverasagen- :eral rule there 1 is no -when thescontacts separate-s0 that-sparking current flow at the moment rtroubles,-are-.avoided. I

The invention :will be better understood from the .followingdescription of a preferred-:method of carrying :it .into effect which should be taken in conjunction with the: accompanying drawings. -By:thesedrawings,--Eig. .1 shows diagrammaticallyasufficient. of the; electrical circuits toenablethe inventionto be understood and the gen- .eral plan-of-fthe control arrangements. may-for instance be similar to that disclosed in-.British patent-specification Nos."541,658-.and 512,439;- and T Figsifz through 5,-inclusive. when arranged sideby side, show the circuit. connections of a fivephase controller-embodying the principlesjof ..the invention-with it. being noted that Figs.- 2,

3 2.116.355 are-substantial-duplicatesof Figswl, 2 and 4sof Britishpatent specification No. 512,439,

andEig5,4:ineorporateswith the showing of -Fig. 3

of the said British patent that showing which is made in Fig.1 thereof.

".Theconta'cts-AR'C.and-AFC are assumed to :belong to a detector associated-with phase A-and these :contacts: may-.be pneumatically operated iromra tread -mem-ber providedwith two longiwtudinal'cavities of the typeshown in Britishpatexit-specification No. 512,836., AB is thesorcalled respectively are the road relayy-AP', and '-AS Shown in. Figs. 2. and 4 primary and-.secondary-phas- 'ing relays for this phase, while EX istheso-called extension relay-which may be common to all the phasesandcanbe suitablyl associated therewith I cut specification No. 541,658 previously ,lmen- .abyt appropriate; cross-connections .at .the frame CCF. w

---'As may be, seen fromreference to .Britishpattioned, relay .AP is. operatedwhen the camshaft next reaches thev vehicle. extension ,positionafter a demandhas. been put... in by. the. operation of the road relay-AR and remains. operated. until the same position is reached after thephasein question receives right of way. Relay ASis, operatedv While-13118. phase: isnactually. receiving the ztgreen signal-and for the subsequent amber leaving. signal.

The capacitor. QA which may have .a value. of 4; mi. .is shunted .by..a resistor. RAI

of comparatively high value, for instance..30,000 ohms; while the relay AR is adapted to be shunted wby aresistor RAZpf comparatively .low value, for

instance 300-ohms.

- Assuming that right of way is held by some a! other-phasesothat the, equipment isintheposi- .tion shown, capacitonQAwill be. discharged. If a vehicle now arrives on the A phase, the contacts AFC will be closed and there'will be a rush of current through the upper winding of relay AR to charge the capacitor and this current surge will operate the relay. It thereupon locks up over its lower winding and by means of other contacts (not shown) puts in a call to transfer right of way to this phase when the requirements of the other phases have been sufiiciently met. Shortly thereafter and while contacts AFC still remain closed, contacts ARC will be closed so that a shunt is placed round the upper winding of relay AR but without any effect since it is locked up over its lower winding. The charge on the capacitor QA will gradually leak away through the resistor RAI after the contacts are opened. If the detector is again operated before right of way is received, no effect will be produced by the repeated energisation of the upper winding of relay AR since the relay is already operated. In due course right of way is transferred to phase A and relays AP and AS are operated thereby releasing relay AR. The detector contacts AFC and ARC are now transferred to relay EX which is connected up similarly to relay AR except that it has only one winding. Hence for each detector operation, relay EX is operated for a predetermined period due to the current surge through capacitor QX regardless of the time of closure of the contacts AFC and ARC. Relay EX in known manner serves to secure repeated extension of the right of way period up to a maximum value if the trafiic is sufficiently heavy. o

If a fault should develop so that contacts AFC and ARC remain permanently closed, relay AR will be re-operated as soon as relay AS is released when phase A loses right of way and consequently right of way will be returned thereto as soon as the other phases have been dealt with. When relay AS is again operated however, the contacts AFC and ARC control relay EX but in the circumstances are only able to produce a single operation of this relay when relay AS first operates, the capacitor QX then remaining charged to substantially the full operating voltage. Hence right of way is not extended up to the maximum as would otherwise happen but only a single extension period is provided by relay EX. Consequently though the phase with which the faulty detector is associated may still obtain right of way when there is no traffic to justify it, the period for which this right of way is obtained will be a minimum instead of a maximum. Conversely, even if the trafiic on the phase in question should be heavy, right of way will still be obtained only for the minimum period and to this extent the system does not work according to plan. This cutting down of the maximum period under abnormal conditions is thought to be preferable however to the arrangement in which a maximum period is always obtained even though there may be no traflic at all on the particular trafilc lane in question.

It will be appreciated that the unidirectional feature is obtained in that if contacts ARC are closed before contacts AFC the capacitor QA will already be charged when contacts AFC are closed and consequently there will be no current flow to operate relay AR.

The switch AA is a so-called arterial switch which when operated ensures that right of way returns to this phase even in the absence of traffic. It will be appreciated that the effect of a short-circuited detector is substantialy the same as that produced by the operation of the switch AA, that is to say right of way will always be brought back to this particular phase but no extension up to maximum is automatically produced;

A reference to Figs. 2 through 5 of the drawings may now be had for a description of the operation of the complete apparatus. The vehicle detecting arrangement depicted by Figs. 2 through 5 is designed to operate for five trafllc phases which are depicted as A through E. The showing in British patent specification No. 512,439 also may be referred to for a fuller understanding of the depicted apparatus.

Referring now to the circuit of Figs. 2-5, this as shown caters for five trafiic phases designated A to E. The camshaft which is operated by a solenoid SOL has three positions, position 1 corresponding to the so-called initial interval for the phase associated with the common equipment, that'is to say, the phase which has right of way, hereafter abbreviated R. O. W., and positions 2 and 3 corresponding to the vehicle and amber intervals respectively. The three camshaft, positions are common to all phases, the phases being connected to the common equipment in a cyclic order if demands for R. O. W. are made on every phase. Contrary to ordinary camshaft controller practice, any phase not requiring R. O. W. has no effect on the camshaft cycle thus eliminating quick-stepping and the consequent delay. in transferring R. O. W. which might be appreciable in the case of a transfer between widely separated phases. Each phase of trafiic has four relays associated with it, a demand relay such as AR operated from a roadway detector, a primary phase relay AP and a secondary phase relay AS with its relief relay ASR. Relays CM, R, ST and EX form part of the common equipment as do also relays A and B which are connected in series with the neon tubes FA and FE and serve to control the stepping of the camshaft. The positions in which the various cam contacts CI, C2, are closed are indicated by the figures marked therein.

In connection with the electric supply to the equipment the timing circuits are, as is usual,

operated from direct current supplied to the terminals marked plus and minus while the remainder of the equipment with the exception of the vehicle detecting relays is assumed to be operated from an alternating current mains supply, one conductor of which is connected to earth. The corresponding terminal is indicated by an E in a circle and a square while the other terminal of the mains is indicated by the conventional alternating current symbol.

Alternating current at a comparatively low voltage is assumed to be provided for use in the vehicle detector circuit, the terminals concerned being indicated by the usual earth symbol and the conventional alternating current symbol.

For the purpose of the circuit description it will be assumed that R. O. W. is with phase A and that the camshaft is standing in the vehicle interval position 2. If no traific arrives 'on the other phases, R. O. W. will remain with phase A and it will be understood that relays AS and ASR, Fig. 4, which were previously operated in the initial interval position 1 of the camshaft, remain locked during this time and light the phase A green lamp GA, red being shown to all other phases. At armature cs4, Fig. 2, a charging circuit is completed from positive by way of cam contacts C4 over the phase A vehicle interval adjusting switch AVS and common tapped resistance I 0 for condenser QA of the so-called A timer to the next'position. It will be seen that on every signal change some extension of the amber period is produced if a vehicle on the phase'losing right of way operates a detector during the'amwhich renders the manual push button effective serves also to open the vehicle interval and maximum timing circuits and to put in a permanent call on each phase. Right of way will therefore be given toall the phases in cyclic order and the amber'and initial interval signals will be terminate the vehicle interval.

The switches designated ASA, ASB, in the vehicle detecting circuits are so-called timed as usual, the manual control serving to arterial switches and when operated ensure that R. W. will return to the associated phase even in the absence of traflic thereon. Their effect is to simulate the operation of the detector pads at a time when the road in questionis not receiving RVO. W., but owing to the fact that they have no contacts in the A timer circuit they do notproduce any extension effect when the road has R. O. W.

Consideration will now be given to the conditions when the controller has been out of action and'is switched into service by the connection of a current supply thereto.

Assuming first that the camshaft is standing in position 1 relay CM, Fig. 5, which is only required for these conditions nowcperates immediately, locks up over armature cm! and connects operating potential to the chain circuit for the primary phase relays AP-EP at armature cm2. Moreover since all the secondary phase relays are de-energized red is displayed to all approaches to the intersection. Relay ST however is operated over cam contacts C5 and since a charging circuit will be completed by way of cam contacts C2, armatures cpl, dpi, cpl, Mal and up! and comparatively low resistance YA to charge condenser QA of the A timer circuit, relay A will almost immediately be operated to step the camshaft to the vehicle interval position 2.

No'further' operations take place until a call is received from say phase A whereupon relay AR timing circuitbut without any display of amber. Relay CM would-then have been operated and the camshaft quickstepped to position 2. On the subsequent arrival of a vehicle, the camshaft would have stepped to position 3 and normal operation would have been resumed as described above.

In case the camshaft has been stopped in position 2, no change would have been produced when the power wasswitched on except the lighting of the red lamps. When a call was received however the camshaft would step to position 3 and subsequent operations would be as just described.

As previously mentioned, the fact that relay AB is operated by a surge of charging current ensures that in normal practice when the contacts AFC and ARC are opened, the current flow is negligible so that no difiiculties occur with sparking. A further point is that use may safely be mode of relays designed for less than the full operating voltage and this results in fast operating characteristics. The invention accordingly provides an important additional feature of safety in that certain forms of fault which cannot be entirely excluded are arranged to have very little adverse effect on the general efliciency of the system.

We claim:

1. In a traffic control system, a unidirectional detector comprising first and second contacts arranged to be closed successively due to the passa e of a vehicle and in an order dependent on the direction of travel of said vehicle, further contacts, means for operating said further contacts, a source of current, a relay, a capacitor, circuit connections whereby on the closure of said first contacts when said further contacts are closed said capacitor is connected in series with said source of current, said first contacts, said further contacts and said relay, a resistor, and circuitconnections whereby on the closure of said second contacts said relay is shunted by said resistor whereby said relayis momentarily operated by the charging current of said capacitor operates and at armature m3 completes a circuit for relay AP and at armature arZ energizes relay ST. Since a further quick stepping circuit has already been completed by way of resistance YA, armatures cs4, bs4, dsd and cs4 and contacts C45, relay A now again operates and the camshaft is advanced to position 3. Owing to the operation of relay AP, amber will now be displayed to phase A as well as red and the amber period will be timed in the usual manner after which the camshaft will be advancedto position 1. In position 1 of the camshaft, since relay AP is operated, relays AS and ASR are operated over contacts OH to show green to phase A while re-. -lay CM is released by the operation of armaiture. asl. "The initial interval is now timed in camshaft would have been advanced to position 1 after a period timed by the usual amber if said first contacts are operated ahead of said second contacts but not if said second contacts are operated ahead of said first contacts, the periods of operation being substantially independent of the length of time during which both said first contacts and said further contacts remain closed.

2. In a trafilic control circuit of the type claimed in claim 1, a high resistance element connected in shunt with thecapacitor to limit its charged period in the absence of detector operation.

3. In a trafic control system for giving right of way to a plurality of traflic lanes in turn in dependence upon the operation of vehicle detectors located in the respective trafiic lanes, first and second detector contacts arranged to be closed successively due to the passage of a vehicle in a trafiic lane and in an order dependent on the direction of travel of said vehicle, a source of current, a first relay, a capacitor, circuit connecated ahead of said second detector contacts but not if said second detector contacts areoperated ahead of said first detector-contacts, contacts operated by said first relay for initiating the transfer of right-of-way to said traffic lane. a second relay, means for operating said second relay when right-of-way is given to said traflic lane, a third relay, a second capacitor, contacts controlled by said second relay whereby said first and second detector contacts are disconnected from the circuit of said first relay, and associated with the circuit of said third relay, circuit connections whereby on the operation of said first detector contacts when said second relay is operated said third relay is connected in series with said source of current, said first detector contacts and said second capacitor, a second resistor, circuit connections whereby on the operation of said second detector contacts said third relay is shunted by said second resistor whereby said third relay is momentarily operated by the charging current of said second capacitor if said first detector contacts are operated ahead of said second detector contacts but not if said second detector contacts are operated ahead of said first detector contacts, the period of operation being substantially independent of the length of time both said first detector contacts and the contacts of said second relay remain closed.

4. The traflic control system claimed in claim 3 comprising, in addition, a relay locking circuit including a second relay winding for maintaining the relay in operated state.

5. The traflic control system as defined in claim 3 comprising, in addition, a distributing frame for the relay for effecting extension to provide for ready variances of phases.

ALAN LESLIE RANGE. ERNEST THORPE.

REFERENCES CITED The following references are of record in the file of this patent;

UNITED STATES PATENTS Number Name Date 1,976,369 Platte Oct. 9, 1934 2,442,427 Mullerheim June 1, 1948 

